Composite board



11 4 A. R. WELCH 2,200,650

COMPOSITE BOARD Filed April 10, 1957 Fig. 3

Wpfimm (lttorneg Patented May 14,1940

UNITED STATES; "PATENT OFF-ICE 4 Claims.

The present invention relates to a board which hasqualities oflightness, adequate strength'for many structural purposes, and whichconstitutes a sound-proof material which can be incorporated in lightpartitions, doors, and the like. It may also incorporate a fireproof orfire-resistant material.

It is one of the objects of my present invention to devise a boardhaving the characteristics indicated, and one which can be made up inpart from materials which are largely waste in the lumber industry, suchas wood chips or sawdust, and which can therefore be made inexpensively.

It is a further object to provide a board of the character indicated,which can be made up conveniently by the process described in mycopend-'- ing application Serial No. 123,551, filed February 1, 1937.

In a specific application of the principles of this invention it is anobject to provide a board having many characteristics of plyboard inthat it is formed with two faces of wood veneer, and

which has between the faces a filler of compressed wood particles with aresin binder incorporated, so that the board may be formed in a singleoperation by the application of heat and pressure.

Not all resins will serve as a binder in conjunction with thefireproofing agent which has been found suitable, hence it is a furtherobject to provide a composite board, or materials for use in such aboard, which incorporates both a fireproofing material and a binderwhich will work properly under the conditions encountered in themanufacture and use of such a board, when such fireproofing material isincorporated therein.

It is a further object to provide such a board in which may beincorporated spacer element's between the two faces or outer sheets,suflicient to give structural strength and rigidity, but with thelighter and more sound-proof filler material filling a considerable partof the space between the two faces.

It is an object to provide a board, and a process of making the same,wherein because the several components are assembled in the dry state,the harmful effects of steam formation in manufacture are eliminated,and subsequent conditioning is rendered unnecessary.

With these and other objects in view, as will appear hereafter, myinvention comprises the novel board shown in the accompanying draw--ing, described in this specification, and as will be more particularlydefined by the claims.

In the accompanying drawing I have illustrated various forms of theboard, and the process of making the same.

Figure 'l is a perspective view of a corner of a representative board, apart of the top face being broken away to show the interior.

Figure 2 is a similar view of a modified form of board.

Figure 3 is a sectional view through such a board and associated pressparts, showing an initial step in the formation of such a board, andFigure 4 is a similar view showing a further step.

Figure 5 is a similar view showing the process of manufacturing a sheetof aggregated material such as is formed in accordancewith my process.

The board is usually formed of two continuous sheets, I and 2, formingthe opposite faces of the board, which sheets are conveniently of woodveneer.. It should be borne in mind, however, that other materials maybe employed than wood veneer, for instance paper or pulp board might beemployed, or indeed, one or both faces may be omitted. These two facesare held spaced apart, and preferably the spacing is rendered definiteand the entire composite board is stiffened and strengthened by spacermeans which in one form constitutes a marginal frame 3, which may be ofwood. Such a frame, in addition, may serve as part of a mold in thepressing step, later described, even though it becomes a part of thefinished board. Within the marginal frame, and between the sheets i and2, is placed a mass of discrete wood particles, in the dry state, havingincorporated and thoroughly mixed therewith discrete particles, in thedry state, of a binder which sets under heat and pressure, as forinstance a resin. When I speak of wood particles I have in mind woodchips or sawdust, but similar particles having some compressibility, inthemselves or relatively to other particles, may be employed. This massis indicated at 8.

As may be seen in Figure 3, the mass 4, when placed within the marginalframe 3, is of a thickness in excess of that which it is intended tooccupy in the finished board. The initial thickness depends upon' thedegree of density desired, the compressibility of the filler, the amountof pres sure to be used, etc. The lower face 2 may be placed upon apress plate 5, the marginal frame put in place, the mass of particles 4placed within the frame, the face I placed on top of the mass, and thena press plate 6 is placed on top of the face I, and the press plates 5and 6 are moved together to compress the face I down upon the marginalframe 3. The mass 4 of mixed wood particles and binder particles is thuscompressed,

A and when the press plates I and i are heated the entire board isaggregated and held in thiscondition by the setting of the binder underthe influence of heat and pressure, the heat and pressure being such inamount, and continued for such time, as may be required by theconditions (as thickness), or by the particular binder, a number ofwhich are known to be suitable. The formation of the board may beaccomplished by the process and apparatus described in my companionapplication referred to above. This single operation not only solidifiesthe particles of the mass 4, but binds the faces I and 2 to thecompressed mass, and the latter to the marginal frame 3. It will beobserved that the margins of the sheets I and 2 are extended to orbeyond the marginal frame 3, and thus pressure is transmitted directlyto the marginal frame and this is strengthened during the compressingoperation, although the particles of the mass 4 tend to compress in thedirection of the pressure rather than transversely thereto. At finalcompression the board is in a form as shown in Figure 4.

Instead of employing a marginal frame the spacer means may take someother form, as shown in Figure 2, wherein the faces I and 2 are spacedapart by blocks or spacer elements I, which may be arranged in anydesired pattern, preferably interspersed through the entire spacebetween the faces. However, a substantial part of the space betweenthese faces is open, and is filled with the mass of particles at 4. Amarginal frame may be used or may be omitted, as is preferred, in thisform.

A board which is satisfactory for some purposes may be made up with onlya single face, or indeed both faces may be omitted, and the mass ofparticles, as shown in Figure 5 at 8, may be enclosed within a framecomposed of the press plate 9 and the marginal frame I0, and may becompressed by movement toward the plate 8 of a press plate II which fitsclosely within the marginal frame I0, and thus the mass 8 may becompressed and heated and bound into a solid sheet under the influenceof heat and pressure acting upon the binder incorporated with the massof wood particles.

It is at times desirable to render such a board fireproof orfire-resistant, for while its lightness and cheapness recommend it, itis almost entirely of wood, and there are places where a more fireproofmaterial is desirable. I have found that this can be done byincorporating among the discrete particles a fireproofing material. Thatwhich I have used is monoammonium phosphate. To obtain the most intimatemixture thereof with the wood particles, I dissolve the flakes offireproofing material in water, and then moisten the wood particles withthe solution. Care should be taken that they are only moistened,otherwise an excessive amount of steam is formed at pressing.Monoammonium phosphate of about 6% to 7% of the whole mass has beenfound adequate, and a higher percentage has been found not to improvethe results materially.

When the fireproofing material is employed it has been found thatcertain resins or binders will not operate satisfactorily, at least,within the limits of the process of pressing employed. That which hasbeen found most satisfactory is Laucks urea resin, commerciallyavailable as such, although certain resins manufactured by GeneralPlastics, Inc., designated 120 and 470 resins, have been found suitable.

The fire-proofing treatment may or may not be employed, as themanufacturer or user may prefer. If the iireproofingmaterial is omitted,I do not know any resin of the general type setting under heat andpressure that can not be used, provided the limiting conditions, forinstance, time, pressure, and temperature, can be met without injury tothe wooden components of the board.

Such a composite board is light, yet may be given adequate strength forthe purpose desired by the marginal frame or spacer members. It can besawed and nailed like ordinary plywood. It has been found to haveexcellent properties for the manufacture of doors, and doors made ofthis composite board do not permit the penetration of sound to anyconsiderable degree. Similarly partitions can be built of this board,such partitions being light, comparatively thin yet soundproof to aconsiderably higher degree than partitions made of ordinary plyboard orother composite boards.

Because the particles of wood and binder are mixed in the dry state,especially if the fireproofing material is not used, there is no excessmoisture which must be eliminated, at an expense of power (in the formof heat) or time. Even more important, perhaps, is the fact that theformation of steam within the interior of the board is minimized orprevented, hence steam pockets which destroy the homogeneity of thefinal board, or which may blow out or bulge upon release of pressure,are not formed. By reference to wood in a dry state I mean wood whichhas not been subjected to soaking or wetting (other than such asnaturally and unavoidably occurs in usual handling and millingprocesses), and which therefore is in a natural state, although, if agiven wood or mass of particles is found to contain (from natural orartificial causes, or'because of the fireproofing step) an excess ofmoisture, it is not outside the scope of my invention, nor of the termdry state," to reduce the moisture content, before mixing or pressing,by any suitable process. It is preferred that the wood contain somemoisture while being pressed, for a board incorporating moisture islessbrittle or friable than one wherein the moisture content is undulyor unnaturally low. If the moisture content of the particles, or of thepressed board, is too low, it may be necessary to condition the board bysupplying moisture to it, and if the latter can be avoided by leavingthe normal moisture content in the particles, an additional step withits consequent expense and delay can be avoided.

What I claim as my invention is:

1. A process for manufacturing composite boards or the like whichcomprises mixing in a dry state discrete wood particles or the like witha resin binder, placing in a mold, as a first layer, a sheet of plywoodor the like, next placing spacer strips of wood substantially at themargins of the first layer, adding as a second layer, and within thespacer strips, said mixture of wood particles and binder, covering thesecond layer and marginal strips with a sheet of plyboard and thenapplying heat and pressure to the mass, in the mold, for a time and to adegree necessary to aggregate the same into a solidified sheet orcomposite board.

2. A process for manufacturing composite boards or the like whichcomprises mixing in a dry state discrete wood particles with a resinbinder, placing in a mold, as a first layer, a sheet of plyboard, nextplacing on the first layer spaced blocks of wood or the like, thenfilling in the spaces between the blocks with the said mixture of woodparticles and binder, covering this second layer with a sheet ofplyboard and then applying heat and pressure to the mass, in the mold,for a time and to a degree necessary to aggregate the same into asolidified sheet or composite board.

3. A process for manufacturing composite boards or the like whichcomprises mixing in a dry state discrete wood particles or the like witha resin binder, placing in a mold, as a first layer, a sheet of plyboardor the like, next placing spacer elements of wood on the aforesaidsheet,

adding as a second layer, intimately associated with the spacerelements, said mixture of wood particles and binder, covering the secondlayer and spacer elements with a sheet of plyboard or the like, and thenapplying heat and pressure to the mass, in the mold, for a time and to adegree necessary to aggregate the same into a solidified sheet orcomposite board.

4. A process for manufacturing composite boards which comprises mixingin a dry state discrete wood particles or the like with a resin binder,laying up a composite board with a sheet of plyboard or the like as afirst layer, next placing wooden spacer elements on the aforesaid sheet,adding as a second layer, intimately associated with the spacerelements, said mixture of wood particles and binder, covering the secondlayer and spacer elements with a sheet of plyboard or the like, andthen, with the composite board in place in a mold, applying heat andpres-v sure thereto for a time and to a degree necessary to aggregatethe same into a solidified board.

ARTHUR R. WELCH.

